轻质CB/RGO复合涂层的制备及其吸波性能研究

目的制备吸波性能优异的碳基复合吸波涂层。方法采用液相法在导电炭黑(CB)体系中原位生长还原氧化石墨烯(RGO)材料,合成了CB/RGO复合吸收剂,并以环氧树脂为基体制备了CB/RGO复合涂层。利用扫描电子显微镜(SEM)和透射电子显微镜(TEM)对制备的CB/RGO复合吸收剂进行微观结构表征,研究了吸收剂填充量和厚度对涂层电磁性能的影响规律。结果微观结构分析表明,CB以一种类似“葡萄状”的结构形态附着在石墨烯片层之间,在其表面实现包覆性生长,分散均匀且具有较好的附着力;制备的CB/RGO复合涂层质地均匀,密度仅为1.1 g/cm^3,兼具轻质柔性的特征。微波反射率测试结果显示,在高填充量3.0%和3.7%下,涂层均未表现出明显的强电磁吸收能力,而在低填充量1.6%和2.3%下,涂层表现出十分优异的微波吸收性能。结论当填充量为2.3%、厚度为1.9 mm时,涂层表现出最佳的吸波性能,最大吸波强度为−17.1 dB,有效吸波频宽达到6.63 GHz,覆盖整个测量频段的66.3%,显示出良好的宽频吸波性能。另外,当厚度为2.5 mm时,填充量为2.3%的涂层实现了雷达波在X波段的微波全吸收。     

海洋工程用结构铝合金无铬化学转化膜耐腐蚀及涂装配套性能

为改善服役于海洋环境下的结构铝合金的耐腐蚀性及其与底漆的配套性能,在两种典型海洋工程用结构铝合金(5083-H116和6061-T6)基体上制备了一种无铬钛/锆基化学转化膜———Alum-nanoceramic coating。采用扫描电子显微镜(SEM)和能谱仪(EDS)对膜层形貌及组成进行了表征,通过动电位极化曲线和电化学阻抗谱研究了膜层的电化学性能,利用中性盐雾试验及胶带剥离试验分别对膜层耐蚀性及其与环氧厚浆底漆的配套性进行了考察。结果表明:5083和6061铝合金Alum-nanoceramic无铬化学转化膜中性盐雾试验白锈面积达到5%所需时间分别为240h和168h;5083铝合金Alum-nanoceramic膜层比后者显示出更好的与环氧厚浆底漆的配套性能。     

石墨烯改性增强富镁涂层对AZ91D镁合金的腐蚀防护效果

目的 在保证环氧富镁涂层阴极保护作用的同时,降低涂层中的镁粉含量,进一步提高环氧富镁涂层对镁合金基体的保护效果.方法 将不同含量的石墨烯(1％、2％、4％)加入环氧富镁涂层中替代等质量的镁粉来制备改性富镁涂层,利用Machu测试、电化学交流阻抗测试、扫描电子显微镜观察等方法,对改性富镁涂层的防护性能进行研究.结果 石墨烯添加量过多(4％)时,涂层的耐蚀性降低;添加量较少(1％和2％)时,涂层的孔隙率降低,附着力升高,涂层的屏蔽效果得到提高,开路电位测得的阴极保护作用时间也有一定程度的延长,其中石墨烯添加量为2％、镁粉含量为48％时,涂层的阴极保护时间为145 h,改善作用最明显.结论 适量石墨烯加入环氧富镁涂层中增强了镁颗粒与基体之间的电连接,有效提高了涂层中镁粉的利用率,降低了镁合金的腐蚀速度,并且没有改变富镁涂层中镁粉的作用机制.同时,由于石墨烯片层状结构和较小的粒径,填充了涂层中的孔隙,并且在涂层中形成迷宫结构,有效延长了电解质的扩散通道,使涂层屏蔽性能得到提高.     

Comparison study on anticorrosion performances of the epoxy coatings with two different nano‐polyanilines for Q235 steel

Sulfuric acid doped nano‐polyaniline was prepared by direct mixed oxidation in two different systems. A novel approach for preparing polyaniline (PANI) in FeCl₂/H₂O₂ system was developed. The PANI possessed an excellent dispensability. Corrosion protection of epoxy coatings containing two kinds of polyaniline (PANI) on Q235 steel was studied by electrochemical impendance spectroscopy (EIS) technique and Tafel polarization test in 3.5 wt% sodium chloride (NaCl) aqueous solution. The results indicated that the epoxy coating containing PANI obtained in FeCl₂/H₂O₂ system had the best performance of the corrosion protection among three systems under investigation. The possible protective mechanism of PANI was discussed.     

The effect of epoxy coating containing emeraldine base and hydrofluoric acid doped polyaniline on the corrosion protection of AZ91D magnesium alloy

Corrosion protection of epoxy coatings containing emeraldine base polyaniline (PANI) or hydrofluoric acid doped PANI on AZ91D magnesium alloy were studied by EIS and Pull-Off Adhesion Test. The results indicated that the addition of emeraldine base PANI or hydrofluoric acid doped PANI could improve the corrosion resistance of epoxy coating. The epoxy coating containing hydrofluoric acid doped PANI had the best performance of the corrosion protection among three systems under investigation. The corrosion product film was analyzed by XPS indicating that PANI changed the chemical structure of the corrosion film. The protective mechanism imparted by PANI was discussed.     

聚苯胺/环氧涂层对AZ91D镁合金耐蚀性能的影响

通过化学氧化法合成本征态及氢氟酸掺杂态聚苯胺(PANI),用红外光谱对其结构进行表征。以环氧树脂为成膜物质,在AZ91D镁合金基体上制备了本征态及氢氟酸掺杂的 PANI/环氧涂层,用EIS方法研究涂层在3.5%NaCl溶液中的耐蚀性,并用SEM对浸泡后基体表面形貌进行观察。实验结果表明,与环氧清漆相比,本征态PANI的加入明显改善了环氧涂层的耐蚀性,而氢氟酸掺杂后进一步提高了PANI/环氧涂层的性能。用XPS对基体表面分析,发现添加聚苯胺的涂层在镁合金表面形成了具有保护作用的产物膜。     

Polyaniline-lignosulfonate/epoxy coating for corrosion protection of AA2024-T3

Corrosion protection arising from epoxy coatings incorporating lignosulfonate-doped polyaniline (Pani-LGS) upon AA2024-T3 was studied in 0.6 M NaCl. Synthesized Pani-LGS particles were investigated using TEM, FTIR, TGA and conductivity, whilst coatings were also physically examined using SEM. The coating performance was studied using a combination of potentiodynamic polarisation, EIS, FTIR spectroscopy and X-ray photoelectron spectroscopy. The performance of Pani-LGS/epoxy blends is discussed more generally, with tests revealing that on exposure to 0.6 M NaCl solution for 30 days, a 5 wt% Pani-LGS/epoxy coating resulted in low levels of corrosion. A mechanism for the postulated mode of corrosion protection is presented.     

Study on corrosive electrochemical behaviors of zinc‐rich and graphite‐filled epoxy coatings in 3.5 wt% NaCl solution

Environment behaviors and degradation mechanisms of two organic epoxy coatings coated on carbon steel sheets in 3.5 wt% NaCl neutral solution were studied by electrochemical impedance measurements and atomic force microscopy (AFM). The results showed that the coating resistance (R_p) of the graphite‐filled epoxy coating tested, which presents the film barrier performance, is higher than those of 6101 epoxy resin for initial seawater immersion, but the coating resistance of the zinc‐rich epoxy coating was lower than that of 6101 epoxy resin. After salt spray tests, zinc‐rich epoxy coating coated on the metal still has good anti‐corrosion performances due to the existence of protection effects called “electrochemical” and “chemical” protection. Those behaviors and degradation mechanisms of two coatings can be explained by a series of measured electrochemical impedance spectroscopy measurements, and two equivalent circuit models were proposed to explain the degradation processes of the two organic coatings.     

间苯二胺-氧化石墨烯/有机涂层的制备及防腐性能研究

针对有机涂层中氧化石墨烯(GO)分散性差、与树脂相容性不好的问题,本工作选择间苯二胺作为"桥接物质",利用其分子上的两个胺基与GO和环氧树脂的环氧基团分别键合,从而改善GO与环氧树脂间的相容性。同时,利用间苯二胺的空间位阻效应有效改善了GO的团聚问题,提高在环氧树脂中的分散性。采用化学接枝法得到间苯二胺表面改性的GO(M-GO),并制备了M-GO与环氧树脂E-44复合涂料(EP/M-GO)。结果表明,间苯二胺的胺基能够成功与GO表面的环氧基团键合,且在透射电镜下可以观察到M-GO呈现出少量片层的状态,团聚现象明显改善。另一方面,涂层截面形貌表明M-GO与基料树脂之间结合良好。复合涂料在12 d的盐雾实验后仍然能够为金属基底提供保护,且浸泡1000 h后的阻抗模值(|Z|0.01 Hz)仍可达109数量级,防腐性能明显提高。     

Corrosion inhibition of aluminum alloy in chloride mediums by undoped and doped forms of polyaniline

Corrosion inhibition of Al 3003 alloy by pure undoped PANI (emeraldine base) and PANI doped with p-toluene-sulfonic, camphorsulfonic and dodecylbenzenesulfonic acids was investigated. Corrosion resisting properties of PANI coatings with an artificially created hole defect were evaluated by electrochemical impedance spectroscopy (EIS) in aqueous 3.5% NaCl and 0.1 N HCl solutions. The highest corrosion inhibition factor was obtained for undoped PANI being equal to 12 and 4.4 in neutral and acidic media, respectively. The results indicated that corrosion protection of the bare aluminum alloy surface resulting from a defect of the PANI coating is in line with an increase of the thickness of the oxide layer protecting the aluminum alloy surface. The efficiency of corrosion protection of mild steel and aluminum alloy by polyaniline coatings was compared.     

Enhanced thermal diffusivity of copperbased composites using copper-RGO sheets

The synthesis of copper-reduced graphene oxide (RGO) sheets was investigated in order to control the agglutination of interfaces and develop a manufacturing process for copper-based composite materials based on spark plasma sintering. To this end, copper-GO (graphene oxide) composites were synthesized using a hydrothermal method, while the copper-reduced graphene oxide composites were made by hydrogen reduction. Graphene oxide-copper oxide was hydrothermally synthesized at 80 °C for 5 h, and then annealed at 800 °C for 5 h in argon and hydrazine rate 9:1 to obtain copper-RGO flakes. The morphology and structure of these copper-RGO sheets were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. After vibratory mixing of the synthesized copper-RGO composites (0-2 wt%) with copper powder, they were sintered at 600 °C for 5 min under100 MPa of pressure by spark plasma sintering process. The thermal diffusivity of the resulting sintered composite was characterized by the laser flash method at 150 °C.     

Corrosion performance of epoxy coatings modified by nanoparticulate SiO2

Electrochemical impedance spectroscopy (EIS) was employed to investigate the corrosion performance of nanoparticulate SiO₂ modified epoxy coatings on carbon steel in 3.5 wt% NaCl solution, coupled with salt spray test. Capacitance‐gravimetric methods and delamination tests were performed to analyze the water uptake behavior and interface stability against delamination of modified coatings, respectively. Four systems were studied, including a clear coating and three pigmented coatings (with 1, 2, and 3 wt% nanoparticulate SiO₂). The experimental results showed that nanoparticulate SiO₂ particles can improve the anti‐corrosion performance of the coatings and the optimal addition content is 2 wt%. The results obtained with capacitance‐gravimetric measurements showed that the diffusion process of water through epoxy coatings with different pigment volume concentration (PVC) obeyed the second Fick's diffusion law in the initial period. Adding nanoparticulate SiO₂ into epoxy coatings can act effectively. The positive influence is attributed to the reaction between nanoparticles and epoxy resin which is confirmed by FTIR, improving the barrier and dispersion effectiveness of coatings. The negative one is increasing the number of pores in the coatings when the adding amount is beyond the critical PVC.     

Enhanced Mechanical Properties of AA5083 Matrix Composite via Introducing Al0.5CoCrFeNi Particles and Cryorolling

High-entropy alloy particles (HEAPs) can markedly enhance the mechanical properties of metal matrix composites (MMCs). In this study, AA5083/Al_0.5CoCrFeNi HEAPs MMCs with different HEAPs contents (0, 1, and 3 wt%) were prepared via a stir-casting, and then these MMCs sheets were hot rolled (573 K) and cryorolled (77 K), respectively. The mechanical properties of the MMCs sheets were measured by tensile testing and microhardness test. Additionally, their microstructures were analyzed by scanning electron microscopy and transmission electron microscopy. Results revealed that the ultimate tensile strength (UTS) of the as-cast AA5083/Al_0.5CoCrFeNi HEAPs MMCs were improved from 203 to 257 MPa by adding 3 wt% HEAPs. And the mechanical properties of the MMCs sheets were improved after cryorolling. After cryorolling with 50% rolling reduction ratio, the MMCs with 1 wt% HEAPs had an UTS of 382 MPa, which was 1.9 times that of the MMCs before rolling. Finally, the strengthening mechanisms of HEAPs and cryorolling on the AA5083/HEAPs MMCs were discussed.     

Understanding electrodeposition of polyaniline coatings for corrosion prevention applications using the wire beam electrode method

Polyaniline (PANI) films have been successfully electrodeposited on aluminium AA1100 electrode surfaces in acidic electrolytes as anti-corrosion coatings. The wire beam electrode (WBE) has been applied for the first time as a novel tool to monitor the electrodeposition processes; and also to understand the anti-corrosion performance and mechanism of the PANI coatings. During PANI electrodeposition, the WBE was polarised anodically, and anodic polarisation currents were measured from various locations over the WBE surface to produce anodic polarisation current maps (APC maps). Preliminary experiments have revealed that if an AA1100 electrode was not pre-treated, APC maps would show a localised anodic current distribution, resulting in a nonuniform PANI deposit. If the AA1100 electrode was pre-treated by a cathodic polarisation process, APC maps would show a random anodic current distribution, leading to a PANI coating covering the whole electrode surface. When exposed to a corrosive environment, PANI coatings were found to prevent localised corrosion of AA1100, primarily by enhancing its passive film rather than by a barrier mechanism. However, a nonuniform PANI coating has been found to accelerate general corrosion of AA1100. These results suggest that the WBE is a practical tool for monitoring, characterising and optimising PANI electrodeposition processes and for evaluating the anti-corrosion performance of PANI coatings.     

Effect of polyaniline–montmorillonite nanocomposite powders addition on corrosion performance of epoxy coatings on Al 5000

A series of polyaniline (PANI)/montmorillonite (MMT) nanocomposite materials has been successfully prepared by in-situ emulsion polymerization in the presence of inorganic nanolayers of clay with camphorsulfonic acid (CSA) and ammonium peroxydisulfate (APS) as surfactant and initiator, respectively. The nanocomposite materials were characterized by Fourier Transformation Infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Epoxy resin was used as a binder for the nanocomposites in order to obtain a thick and uniform coating. In order to understand the effect of MMT and PANI on the corrosion inhibition performance of the epoxy coatings in 3.5% saline solution at 65 °C, the epoxy (E), epoxy blend with polyaniline (EP), epoxy blend with polyaniline and MMT (EPM) coatings were investigated by electrochemical impedance spectroscopy (EIS). The results showed that EPM coatings with 5% clay on pretreated aluminum by anodizing were much superior in corrosion protection, with respect to the other samples. Incorporation of PACN nanocomposites inside the epoxy significantly increases the resistance of the coating in comparison to the other coatings in 3.5% saline solution at 65 °C. These phenomena can be attributed to specific morphology of the nanocomposite.     

石墨相碳化氮复合材料的制备及其可见光光催化性能的研究

目的提高半导体石墨相氮化碳(g-C_3N_4)的光催化性能。方法通过Hummers法和半封闭一步热裂解法制备了氧化石墨烯(GO)和g-C_3N_4,再分别利用溶剂热法、热缩聚法和浸渍化学还原法制得相应的TiO_2/g-C_3N_4、ZnO/g-C_3N_4、RGO/g-C_3N_4复合材料。采用X-射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外-可见漫反射吸收光谱(UV-Vis DRS)和傅里叶变换红外光谱(FT-IR)等手段对复合材料进行表征,并以降解罗丹明B(Rh B)来评价其在可见光下的光催化性能。结果以尿素与三聚氰胺的混合物为原料通过热裂解法制备的g-C_3N_4,比使用纯尿素制备的g-C_3N_4具有更优的催化效果。TiO_2、ZnO、RGO的引入提高了g-C_3N_4的光催化活性,Rh B的降解率分别为95.6%、95.0%、78.1%。RGO质量分数为2.0%时,RGO/g-C_3N_4复合材料的催化效率最高。结论通过g-C_3N_4特殊的能带调控优势与TiO_2、ZnO、RGO的协同作用,提高了复合材料在可见光区的吸收强度和电子传导能力,进而提高了在可见光下的光催化性能。     

One-pot hydrothermal synthesis of ruthenium oxide nanodots on reduced graphene oxide sheets for supercapacitors

Ruthenium oxide nanodots have been deposited on reduced graphene oxide (RGO) sheets homogeneously by hydrothermal and annealing methods. Adding NaOH solution in GO colloids prevents the restack and agglomeration of GO sheets when mixed with ruthenium chloride solution. Local crystallization of RuO₂ in the composites is revealed by X-ray diffraction and transmission electron microscopy. The element mapping image demonstrates the uniform distribution of Ru on RGO sheets. Unlike the pure crystalline RuO₂ exhibiting poor electrochemical performance, the composites present superior capacitive properties. The hydrothermal time is optimized and a maximum of 471 F g⁻¹ is measured in the composites at 0.5 A g⁻¹ when loaded with 45 wt% of RuO₂. After 3000 cycles, its specific capacitance remains 92% of the maximum capacitance. Our results suggest potential application of the reduced graphene oxide/ruthenium oxide composites to supercapacitors.     

5083 铝合金环氧涂层盐水浸泡失效研究

目的研究铝合金基体上环氧涂层在盐水浸泡环境中的电化学阻抗谱变化规律,揭示涂层失效的原因和机制。方法采用电化学阻抗谱技术、红外测试、扫描电镜及能谱分析等方法,研究涂覆在5083铝合金基体上的环氧涂层在盐水浸泡过程中的裂化过程和失效机制。结果在3.5%(质量分数)Na Cl溶液的连续浸泡下,涂层电阻明显下降、电容明显增大,相应的涂层孔隙率和吸水体积百分数均逐渐增加;长期浸泡后,涂层孔隙率和吸水体积百分数均趋于稳定。随着浸泡时间的增加,涂层表面孔洞等缺陷增多,保护作用减弱;涂层内氧元素含量逐渐增加,碳元素含量逐渐减小;涂层内有羟基生成和C—O键的断裂发生。结论环氧涂层中环氧官能基团在电解质溶液中发生水解,水解形成羟基和氨基等亲水基团以及涂层中存在的孔洞等缺陷,进一步促进电解液的渗透,加速涂层的劣化。金属基体表面腐蚀反应会促进涂层与基体的剥离,腐蚀产物在涂层内的累积,也会导致涂层内孔隙和缺陷增多,促进涂层劣化。     

Fabrication of RGO/Cu composites based on electrostatic adsorption

To address the issues of reduced graphene oxide (RGO) dispersion in copper (Cu) matrix and interface bonding between RGO and Cu, an electrostatic adsorption method with interface transition phase design was employed to prepare the RGO/Cu based composites. Cu-Ti alloy powder was employed to improve the combination by forming carbides at the RGO-Cu interface. It was noted that the mechanical property of 0.3wt.%RGO/Cu-Ti composite was increased by 60% compared with that of the matrix. Strengthening mechanism analysis suggested that the enhancement of the mechanical property was ascribed to the load transfer and second phase strengthening which were from the improved dispersion of RGO and the in-situ formed titanium carbide phase.     

Preparation and corrosion protective properties of titania‐containing modified self‐assembled nanophase particle (TMSNAP) sol–gel on AA2024 aluminum alloy

A new method of preparing water‐based sol–gel containing titania nanoparticles for the protection of aluminum alloy AA2024 against corrosion was presented and performance of the coating in Harrison's solution was studied. The coating was prepared using alkoxysilanes, tetraethylorthosilicate (TEOS) and 3‐glycidoxypropyltrimethoxysilane (GPTMS), and in additional metal alkoxide, titanium(IV) tetrapropoxide (TPOT), as a source of titania particles. Poly(ethylene imine) (PEI) polymer was utilized to create cross‐linking and also to improve the coating quality. In addition, the molar ratios and amount of components and factors affecting performance were assessed to improve coating properties and its performance. Potentiodynamic scan (PDS) and electrochemical impedance spectroscopy (EIS) measurements were performed to evaluate the corrosion protection performance of coatings. Also, scanning electron microscopy (SEM) was employed to investigate surface morphology. The stability of the best prepared coating and its corrosion protective effects on the alloy were evaluated in Harrison's solution up to 15 days. The results revealed that this new sol–gel coating provides significant protection against corrosion of the AA2024 alloy in Harrison's solution.